1. Technical Field
This application generally relates to routing, and more particularly to fault tolerant routing techniques.
2. Description of Related Art
Messages may be communicated between different components in one or more networks of varying topologies using a switch fabric. The switch fabric may include one or more switches and other components arranged to permit transmissions of messages between different components or endpoints. Messages may also be referred to as frames and may include a header portion and a payload, such as data.
Different techniques may be used in connection with routing a message at each juncture, such as by a switch, from a source to a destination endpoint. One technique may be referred to as destination routing in which the destination is used by each switch to make routing decisions such as in connection with a packet-switched fabric. The switches may perform static routing using preconfigured information included in a routing table. The routing tables contain information mappings established by the network administrator before the beginning of routing. These mappings do not change unless the network administrator alters them.
One drawback with using static routing techniques occurs when there is a problem with a link used for one or more paths between a source and destination. With static routing, any designated routes through a down connection fail. Static routing is not able to adjust to the foregoing or other changes in a network without adjustments to the static routing tables. Because static routing techniques cannot react to network changes, dynamic routing techniques may be used which adjust to changing network circumstances by analyzing incoming routing update messages. If the message indicates that a network change has occurred, the routing software can recalculate routes and send out new routing update messages. These network update messages permeate the network, stimulating routers to rerun their algorithms and change their routing tables accordingly. However, dynamic routing techniques may not be appropriate or desirable for one or more reasons related to the added complexity and interaction between routers in order to obtain up to date information about network traffic and topology. Additionally, dynamic routing determinations, for example due to a down connection, that select a routing alternative take an amount of time to perform the selection processing and make effective an alternative route. During this amount of time until the alternative is made effective, transmissions designated to use the down connection will still fail.